The present invention relates to an apparatus for detecting the position of an attachment employed in industrial vehicles such as forklift forks.
An industrial vehicle employs attachments to carry and transfer loads. For example, a forklift employs forks, which are supported by a forklift mast, to carry loads. It is important that the position of the forks be detected to guarantee vehicle stability.
A limit switch is often installed in a forklift to detect the position of the forks. The limit switch is actuated depending on whether the forks are located above or below a predetermined position.
A typical limit switch has a body on which an actuating piece, which is moved by external force, and a switch mechanism is arranged. Displacement of the actuating piece moves the switch mechanism and actuates the limit switch. That is, the limit switch is actuated (or de-actuated) when the actuating piece is displaced and de-actuated (or actuated) when the actuating piece returns to its original position. Once a detected body (e.g., forks) enters a certain zone defined either above or below a predetermined position, the actuating piece is kept displaced until the detected body moves out of the zone. In other words, the limit switch is either continuously actuated or continuously de-actuated when detecting the position of the detected body.
In a forklift, the body of the limit switch is fixed to an outer mast. A vertically elongated, plate-like dog for manipulating the actuating piece of the limit switch is fixed to an inner mast. The limit switch and the dog are arranged such that the dog moves the actuating piece to change the state of the limit switch when the forks are located above a predetermined position.
The space between the inner mast and the outer mast is narrow. Thus, the limit switch body cannot be arranged at a location that permits the inner mast to directly manipulate the actuating piece. The inner mast indirectly manipulates the actuating piece with the dog, which is secured to the inner mast. Accordingly, the dog is designed to manipulate the actuating piece of the limit switch appropriately.
However, such a limit switch results in the need for a dog formed exclusively in accordance with the maximum lifting height of each forklift type. This increases the number of parts and raises costs.